In this edition of Digital EOS Essentials we explain all you need to know to capture more consistent exposures

Photo Plus EXPERT

MARCUS HAWKINS

PHOTO EXPERT

Marcus has been passionate about photography for more than 25 years. A former editor of our sister publication Digital Camera, he has written about photography and cameras for a wide range of clients, including Canon and Jessops, and uses a Canon EOS 5D Mk III.

Correcting your exposures

Why your camera meter can get things wrong - and steps you can take to deal with it

Trying to achieve a good exposure with a digital camera is world away from the occasional finger-crossing that came with shooting film. Being able to preview the results on the rear screen and check the brightness range with the histogram means that you know exactly what you’re getting straight out of the camera, and can make any exposure adjustment to ensure you get good results.

And you will need to make exposure adjustments. Despite a top-of-the-range EOS body, such as the 5D Mark IV being loaded with a 150,000-pixel metering sensor that can recognize colour and faces as well as brightness - it is, in effect, a miniature imaging sensor - it can still get things wrong occasionally.

Rather than measuring the that’s falling onto the subject of a photograph, your camera measures the light reflected by the subject into the lens, and this can lead to exposure errors. Camera meters are tuned to approximately 18% grey - they assume that the world is a mid-tone grey that reflects approximately 12-18% of the light that falls on it. Although many scenes average out to an overall mid-tone, there will be plenty that are either darker (and reflect less than 18% of the light that falls on them), or brighter (which reflect more than 18%). Generally speaking, your camera still wants to make an exposure closer to mid-tone, which can result in dark scenes looking too bright and bright scenes looking too dark.